What Are These Arrows (and why are they still here)?

If you’ve used a Windows Mobile phone device, you’ve probably seen the little signal strength icon at the top. If you’re lucky, you live in a place with good signal strength and see many bars. If you’re like me, you live in a cellular dead spot and are happy when you get one bar.

On many non-WM phones, the part of the icon that’s not bars looks something like an antenna–a vertical line with a triangle on top of it. While you sometimes see this antenna icon on WM Phones, it’s often something else. And, what that “something else” is varies from device to device. On some it’s a G. On others it’s an E. On still others it’s two arrows pointing left and right. What are these things? What did they do with our beloved antenna triangle? And why won’t they go away?

It’s all about the data

If your signal strength icon has something instead of an antenna, it means that your device has a network address (an IP address). This means that it can send data to and receive data from the internet. The arrows are our default “data connected” icon. They’re often used by CDMA networks for both 1xRTT connections and EvDO connections. OEMs and Mobile Operators have the ability to customize that icon, and often replace the arrows with other things. GSM devices usually have a small “G” or an “E.” (Don’t confuse these with the larger G or E icon to the left of the signal strength icon. I’ll talk more about those later.) The G usually means that you have a GPRS connection and the E usually means you have an EDGE connection. However, some devices can connect to and get faster EDGE speeds but only show the G icon.

Why doesn’t it go away?

In our 2002 release, when an application requested a connection to the internet, we’d create a connection. Then, when the application said it was finished with that connection, we’d tear it down. In our 2003 release, we changed this behavior to the current one. Once you’ve connected once, it stays connected. We made this change for a number of reasons, not the least of which was that it allowed a much better user experience. In 2002, whenever you wanted any data from the Internet, you had to wait a few seconds for the device to request an IP address from the network. Staying connected all the time means that you get data much more quickly. Also, Mobile Operators requested it. It was more expensive for them to be constantly creating and tearing down connections than to just do it once. Finally, staying connected enabled us to develop a fast “push email” client that relied on the device holding an IP address.

It’s important to understand that we only do this on connections with “Suspend/Resume” functionality. These kinds of connections are suspended when a phone call comes in and resumed again when it is finished.

Doesn’t this cost me money?

In general, no. A long time ago phones sent data over “circuit switched” connections. These were similar to old style modems on your PC. They would make a phone call and send data over that voice connection. The Mobile Operator couldn’t really tell the difference between those calls and other voice calls, so they charged per minute. Current data connections (GPRS, etc), though, are different. For these types of connections, every Mobile Operator that I’m aware of now charges per byte transferred, not per minute. So you can keep your data connection on all the time and only get charged when you send or receive over it.

What about my battery life?

Just having a data connection shouldn’t affect your battery life. Most of the time, the device isn’t doing anything with that connection. It just sits there idle. If you’re sending a lot of data over the connection, though, that will definitely impact your battery life. Unfortunately, the arrows don’t really tell you whether you’re sending data or not (though I’ve seen devices that animate the arrows while data is being transferred).

There’s another box, what does that mean?

Sometimes you see a larger box to the left of the signal strength icon. This one usually says G, E, 1X, or Ev for GPRS, EDGE, 1xRTT, or EvDO. This icon says that the device can see that sort of network, but doesn’t necessarily mean that it’s connected. It’s more of a, “This network is available,” notification than anything else. The icon is often replaced with other notification icons, so you don’t always see it. Its biggest benefit, in my opinion, is that it will tell you on a CDMA device whether you’re currently getting 1xRTT speeds or the much faster EvDO speeds.

Other questions?

That’s pretty much what I know on the subject. But if you have other questions, ask away. I’ll see if I can find answers for you.

Mike, here is one simple question. If we have a data connection open to a server and we are waiting for a response say for up to 15 minutes, but don’t want to be wasting battery power on this – what is the best way to do this at the socket level?

We’ve tried two ways:

Poll the socket every 2 seconds. Bad.

Have the socket command timeout after 15 minutes. This doesn’t seem to work reliably.

I have a T-Mobile MDA and it doesn’t seem to always a connection open. In particular, it seems that whenever ActiveSync connects to my Exchange server to synchronize, it then closes the connection after the sync. Is that something that T-Mobile did? I don’t see a setting in ActiveSync to tell it to disconnect or maintain a connection after a sync.

Maybe I have misread (twice) your explanation. I have 2 WM5 devices, a JasJar and K-Jam. Both do the same thing, which is show the antenna above the bars. Then, the big "G" (disconnected but available data connection) turns to a little G with the arrows, which animate when AS is syncing with the server, but in no other circumstance.

What devices dispensed with the triangle on a pole icon, because these AKU2 Imate’s didn’t.

Frank, it’s certainly possible for TMo to configure its network and devices to not do always connected. However, I’ve never seen them do that. They were one of the original proponents of having us go to the "always connected" model. On your MDA, when it first connects to a GPRS/EDGE connection, you should get a little bubble that pops down from the signal strength icon and stays up for a few seconds. Are you seeing that repeatedly?

MikeH, 1xRTT and EvDO are CDMA technologies (used by Verizon, Sprint, and Korean MOs). UMTS is the followon to GPRS/EDGE and is a GSM technology (used by TMobile, Cingular/AT&T, and pretty much everywhere else in the world). It’s unlikely you’d ever see EvDO and UMTS icons on the same phone. I don’t live in a place with UMTS, so I’ve never seen the UMTS icon. But, if the G for GPRS and the E for EDGE are any indication, I’d guess it will be a U.

Ricardo, the OEM has the ability to change the icons. I’m not aware of any way for end users to do so.

OK, but one further question is, does it show a H in the case of HSDPA?

Another one: In the WM5 SystemState class there is a Phone1xRttCoverage and a PhoneGPRSCoverage property, but there is no PhoneUmtsCoverage or PhoneHSDPACoverage property? Is there any hack to get that info via registry or pInvoke call?

Great information! I own a Q and it shows the little arrows for most of the day but in the evening or after no use for some time I finally get the Antenna Icon. I am not sure why it would revert back to the antenna, Did it lose the connection?

so what happens if you have to use a GSM connection? It means you can’t disconnect? I’m using a hp hw6915 and if you hold down the red end call key to disconnect the GSM connection it disconnects then starts to redial it. We use the GSM connection in places where GPRS is not supported. If we can’t disconnect it will run up huge international phone bills. Any way around this? It seems like no one thought about anything other than using GPRS. Is there any way to add the old disconnect option to the pop up bubble?

Alex, I asked the Active Sync guys what they do. They said that they use an algorithm to figure out what the max timeout on the network is and adjust it dynamically based on network conditions.

Ness, WiFi is supposed to take precedence over cell connections. We have a component called Connection Manager that handles this. It’s possible that the third party that did your WiFi stack didn’t register it with Connection Manager.

MikeH, I can’t even get UMTS here. No idea what they do for HSDPA. (-: I’m guessing it’s H though, as you said. The OEM picks those icons though, so they could do whatever they’d like.

Buzz, whether the connections is always on or times out after so long is up to the mobile operator. I’m not sure if you’re losing connection or if Verizon just makes it timeout. If you do disconnect and something requests a data connection, it should reconnect automatically.

Alan, if your mobile operator has you configured for a circuit switched connection, they should have configured your device to not stay connected all the time.

This is speculation on my part, but it’s possible that the E, U, and H icons aren’t on the phone. Those icons all come from the OEM. If they build an image for a mobile operator that doesn’t support the other technologies, they might leave the icons out.

I am using a Windows Mobile 2003 device in Thailand where GPRS is charged by the minute. I am getting a huge bill due to the the inablity to hang up. I understand it was rectified in WM5. Is there a fix available for 2003?

Ness, WiFi is supposed to take precedence over cell connections. We have a component called Connection Manager that handles this. It’s possible that the third party that did your WiFi stack didn’t register it with Connection Manager.

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"Is supposed" is nice, however, far from reality. I have a HTC TyTN, WM6, and even if Wi-Fi is connected, GPRS is still used to syncronize WIndows Live, maintain Messenger, Direct Push from Exchange etc.

Internet Explorer does use Wi-Fi, but surfing is rarely done on WM and it therefore generates only a fraction of data transfer cost.

The only way to get these services run over WiFi is to disable the phone connection. And on the other hand this clearly shows that none of the data transfer service NEED GPRS, they only need a network route. So why is WiFi not marked as the cheapest route?

GPRS is packet data connection over GSM (2G) network. Speed of connection depends of radio conditions, capabilites of the phone and network settings. Typically, for multislot class 10 phones (for example HTC TyTN), max DL speed is around 86 kbit/s and UL 43 kbit/s (twice less), which uses 4 time slots (channels). Also, most of the phones are class B – cannot have active voice and data connection at the same time, so packet data connection disconnects when making/receiving voice call. GPRS theoretically allows DL/UL of about 160 kbit/s (8 time slots), but the phones capabilities are still limitation.

UMTS is 3rd generation network and it functions in totally different way than GSM. It uses CDMA (Code Division Multiple Access) for channels, but the principle of assigning channels is pretty much the same as GSM, it is just a little bit more flexible. Max. UL/DL 2 Mbit/s.

When you connect packet data connection to GSM, phone sends "GPRS attach" request to network, and when it wants to disconnect it sends "GPRS detach", when it goes to "Idle" mode. In idle mode there is no PDP context and network is not aware of the phone as a packet data node. There is also "Stand-by" mode which is forced by the network after some TIMEOUT PERIOD of connection being idle. In standby mode PDP context is preserved, but the connection needs to switch to "Ready" for data DL/UL.

Most probably Win mobile does a "GPRS attach" and keeps it, and "GPRS detach" only forced by voice call, loss of signal or some error reason. However, when it goes to "Stand-by" it needs to renegotiate to enter "Ready" mode to be able to send/receive. But the point is that when in "Ready" mode, phone has assigned PACKET DATA CHANNELS through which it can send/receive instantly, and in "Standby" it has its IP address and is visible by network, but the channels are NOT ALLOCATED. That means that if some other users have taken all free packet data channels (can happen very often), data flow cannot be established. Only way to keep the phone in "Ready" and keep the channels is to make some traffic before the network timeout. In Europe, traffic is billed in blocks with beginning when entering "Ready" and ending when going out of "Ready", rounded to the next 1kB block, and in roaming rounded to 32kB block.

So, reagarding icons, "E" and "G" belong to the same 2G network, difference is only in channel coding, and mobiles ALWAYS tend to use EDGE ("E"). But, to be more confusing, EDGE has 9 coding schemes of which there are only upper five which are new 8PSK modulation. First 4 are GPRS schemes. It is done probably because of compatibility (remember switch from 80286 to 80386). Schemes are used according to radio conditions – lower number when worse signal. So when the signal has high error rate, when coding drops below 5 – it is actually GPRS. Higher the scheme number is, higher is channel speed. One explanation of letters confusion is that some phones display "E" always when network is EDGE capable regardless of current coding scheme, and some display "E" or "G" according to scheme currently used, even if the network is EDGE capable.

For UMTS (3G) we have only HSDPA – High Speed Downlink Packet Access, up to 14,4Mbit/s (15 channels), but all deployed 3G networks usually have at most 2Mbit/s. But that is only with very good signal when mobile is not moving. When it is in movement, it drops – it has 12 coding schemes. On my HTC TyTN it displays "3G" both in small and big square. But it is European version. In Europe we only have 2G and 3G networks – no analog cellular or other.

In GSM, when you are constantly attached to GPRS, your battery does not spend more energy because there is absolutely no communication between the network and device if there is no data transfer (however there is still periodical normal GSM communication). Only difference is if you are in motion and changing cells in time. Network keeps track of your GPRS connection via "routing area" which consists of one or group of cells. When you switch to cell that belongs to adjacent routing area, there is a, very short, "routing area update" exchange of information between phone and network, regarding GPRS only. But that is very small power consumption.

The same thing is with UMTS. The whole goal of any network is to bring communication traffic to minimum. But, with UMTS, channel coding and transmitting technique is much more complex than with GSM. You are attached to multiple cells at the same time and there is very, very, very strict phone transmit power control. That means that phone must do a lot more signal measurements from group of cells (much more frequent than GSM). It could possibly happen, if you reserved more channels for packet data transfer, that a lot of signalling happens. However, there is a inactivity timeout here which puts you in standby mode as in GSM and then you do not spend battery for packet data at all. But this is all complicated, it depend of many factors: signal strength, network settings, number of users in your location area, etc. .. If the network signal is weak, than any phone in any type of network will eat up your battery.

I have a problem with my ETEN X500+ WM6. Sometimes, GSM signal icon keeps showing that it is searching for a network (…) or even that there is no signal available (!), but the phone is working, and I can even see the signal level (around 20%) using an external plugin.

Anyway to fix this? It would be nice if the icon reflects the real state of the signal.

ok I have the E above the signal bars, the big E to it left and a triangle pointing up on the left of the big E. What is this triangle? it just came from nowere. and it also appear on the operators ballon at the right of t-mobile, above connected.

My personal opinion is that the connection should idle at least over night, or during off-peak times when there is no reconnection so often and the radiations caused by the gprs/3G/EDGE connection could be avoided.

Short question: My Xperia X1 shows a the large available connection types, e. g. G or E, sometimes after a while with thin diagonal crosshatches… what does that mean? Data connectons are not active in this cases.

Mike, what about the Windows mobile icon that looks like three or four z’s? Common sense would dictate the device is not communicating with the network (sleep mode, in a sense), but what prompts that z-icon to appear?